import java.util.StringJoiner;

public class stringjoiner {
    public static void main(String[] args) {
        StringJoiner sj = new StringJoiner(", ","[","]");
        sj.add("aaa").add("bbb").add("ccc");
        int len = sj.length();
        System.out.println(len);
        System.out.println(sj);
    }
}
